This invention is generally in the field of capillary electrophoresis, and relates particularly to apparatus and method for cooling the capillaries of a multiplexed or xe2x80x9cparallelxe2x80x9d capillary electrophoresis system.
Capillary electrophoresis (CE) is a chemical separation technique involving the use of one or more capillary tubes. Parallel CE, a recently developed technique using many parallel capillary tubes, is growing in popularity since this technology allows multiple samples to be analyzed quickly and efficiently. This is particularly advantageous in combinatorial chemistry where many hundreds and even thousands of samples are analyzed over a short period of time. Parallel CE involves the use of a xe2x80x9cbundlexe2x80x9d of capillary tubes, e.g., 24, 48, 96 or other number of such tubes. A chemical sample to be analyzed is loaded in each tube, and a high voltage is applied to the tube, causing the components of the sample to migrate in the tube at different speeds, thereby causing separation of the components which can then be analyzed by conventional light absorption or other techniques. Reference may be made to the following patents and publications for a more detailed description of CE, including parallel CE, and various analytical techniques used in CE: U.S. Pat. Nos. 5,900,934, 5,324,401, 5,312,535, 5,303,021, 5,239,360; C.Culbertson et al., Analytical Chemistry, 70, 2629-2638 (1998); and X. Gong et al., Analytical Chemistry, 71, 4989-4996 (1999). None of these publications disclose the use of parallel CE to achieve chiral separation.
The electrical current passing through the parallel capillary tubes of a CE system can generate a substantial amount of heat, particularly where high voltages and electrical currents are used to achieve the separation of the samples, as during a chiral separation process using chiral buffers, or when CE is run in a micellar electrokinetic chromatography (MEKC) mode where the current is high and the temperature rise in the capillary tubes due to Joule heating can be large. If not dissipated, this heat can cause the formation of bubbles in the samples, sparking, and other undesirable results having an adverse affect on separation and analysis. Therefore, there is a need for a system for effectively cooling such tubes.
Among the several objects of this invention may be noted the provision of cooling apparatus and a related method useful for preventing overheating of the capillary tubes and contents thereof when CE is run in a mode (e.g., an MEKC mode) generating substantial heat; the provision of such apparatus and method having no adverse affect on the separation and/or analytical process; the provision of such cooling apparatus which is adjustable to various cooling temperatures; the provision of such cooling apparatus which can be configured to remove a desired amount of heat; the provision of such apparatus which is safe to use.
In general, this invention is directed to apparatus for cooling a bundle of capillary tubes to prevent overheating of the tubes during a parallel capillary electrophoresis procedure. The apparatus comprises a jacket of thermally conductive solid material comprising mating jacket members movable between an open position in which the jacket members are separated to allow placement of the bundle in the jacket and a closed position in which the jacket members are mated together and the bundle is disposed inside the jacket in thermally conductive relation with the jacket. Window openings in the mating jacket members define a window to permit the passage of light through the window and the capillary tubes of the bundle at the location of the window.
The present invention is also directed to cooling comprising inner and outer jackets. The inner jacket is of thermally conductive, electrically insulating solid material comprising mating inner jacket members movable between an open position in which the jacket members are separated to allow placement of the bundle in the jacket and a closed position in which the jacket members are mated together and the bundle is disposed inside the inner jacket in thermally conductive relation with the jacket. The outer jacket is of thermally conductive solid material comprising mating outer jacket members movable between an open position in which the jacket members are separated and a closed position in which the jacket members are mated together around the inner jacket and in thermally conductive relation therewith. The apparatus also includes a cushion of thermally conductive, cushioning material disposed inside the inner jacket for cushioning the bundle when the inner and outer jacket members are in the closed position. A window is provided through the mating inner and outer jacket members for permitting the passage of light through the window and the tubes of the bundle at the location of the window.
The present invention also involves a method of cooling a bundle of capillary tubes to prevent overheating of the tubes during a parallel capillary electrophoresis procedure. The method comprises positioning a longitudinal section of the bundle in an open cooling jacket of electrically insulating, thermally conductive solid material, and arranging the tubes of the longitudinal bundle section so that the tubes extend generally parallel and in side-by-side relation to one another in a generally planar array in the jacket. The jacket is then closed to enclose within the jacket said longitudinal section of the bundle from one end of the section to the other, said tubes of the longitudinal section being in thermal conductive relation with the jacket. The method also includes initiating a capillary electrophoresis procedure resulting in the generation of heat within the tubes of the bundle, the jacket functioning to cool said longitudinal section of the bundle to prevent overheating of the bundle.
Other objects and features will be in part apparent and in part pointed out hereinafter.